This application is the national phase under 35 U.S.C. xc2xa7371 of PACT International Application No. PACT/JAP99/01899 which has an International filing date of Apr. 9, 1999 which designated the united states of America.
This invention relates to an automatic extinguisher system for buildings, etc., and more particularly to a wet-type sprinkler system of which secondary pipelines are filled with water in a normal condition.
Hitherto, sprinkler systems are in widespread use in buildings, especially in large-scale buildings. In known sprinkler systems, sprinkler heads for fire-extinguish purpose are arranged on ceilings of buildings. The sprinkler system is composed essentially of the sprinkler heads each of which is individually actuated in response to an ambient thermal condition, a feed pump as a water supply unit, and a feed pipe arrangement including primary pipelines and secondary pipelines.
The primary pipeline(s) of the feed pipe arrangement is arranged in a manner perpendicularly rising from the feed pump, to reach the heights of floors. The secondary pipelines are connected to the primary pipeline such that water flows through the pipelines. The secondary pipeline(s) generally extends in the horizontal direction on each floor, and then it is branched and hung-down in the almost perpendicular direction to form hang-down pipe portions, which respectively communicate with the sprinkler heads.
The sprinkler systems with such structures as mentioned above are divided into wet-type sprinkler systems and dry-type sprinkler systems. These two types of the system are different in the following point: That is, in the former type, not only the primary pipelines but also the secondary pipelines are filled with water, and this state is called xe2x80x9cnormal conditionxe2x80x9d. On the other hand, in the latter type, the secondary pipelines are not filled with water, i.e. They are filled with air (in other words, only the primary pipeline is filled with water).
In the known wet-type sprinkler system, water charged in the secondary pipelines in the same manner as in the primary pipeline is constantly kept pressurized, e.g. At 7 to 8 kg/cm2. By this setting, the system has an advantage in that water discharge is quickly performed when the sprinkler head is actuated at the breaking out of fire. In general cases, however, the opening and shutting of the sprinkler heads are controlled not systematically but individually at the ceiling portions at which the sprinkler head are arranged. For example, when a sprinkler head is exposed to heat, a sealed portion thereof is melted, and the sprinkler head comes ready to jet water. Accordingly, in the event that the sprinkler head is actuated on an occasion other than an actual fire, for instance failure of the system or intentional destruction of the same, there is an inconvenience that pressurized water is instantly injected to drench the area around the sprinkler head. For example, when the sprinkler head functions in a wrong way in an office building, documents, computers, elevator systems, etc. Have incurred a huge amount of damage.
To cope with the inconvenience, a wet-type sprinkler system having an additional function of a so-called preliminary operation has been employed. The above-mentioned sprinkler system is provided with a valve section between the primary pipeline and each secondary pipeline. The valve section is caused to normally be closed, and the valve is opened by a control section of the system only when the control section receives a fire-detection signal from a fire sensor (which functions more quickly than the sprinkler head), followed by feeding a large volume of high-pressure water to the secondary pipelines as the preparation for actuating sprinkler heads.
This system only allows water in the secondary pipeline to be discharged in the event of wrong-way-function of the sprinkler heads, and therefore damage can be minimized compared with the prior system. However, the water in the secondary pipeline alone still causes a considerable amount of damage.
On the other hand, the dry-type sprinkler system has been developed to eliminate such damage. Namely, in this system, the secondary pipeline is filled with air which is pressurized at about 2 kg/cm2, in place of water. Therefore, even if the sprinkler head undergoes a failure, only air is discharged, so that damage caused by water can be avoided. This is the largest advantage of the dry-type sprinkler system.
The dry-type sprinkler system requires a work of dewatering or draining the secondary pipe when water injection is carried out on trial. Even after the dewatering work, however, not a little volume of water remains in the hang-down pipe portions if each of the sprinkler heads is not actuated. As a result, it tends that the hang-down pipe portion in the vicinity of a boundary between water and air corrodes, and the corrosion once obtained easily spreads resulting in perforation. To eliminate the corrosion, periodical maintenance and repair are required, or a pipe formed of a special material becomes indispensable, and therefore the defrayal on a managing company is not small.
Further, there is such a tendency that a very small volume of air leaks at a junction of the pipelines, etc., compared with the case where water is stored, so that decrease in pressure of air is relatively fast, which requires frequent addition of air into the secondary pipelines by means of a compressor or the like. The supplement of air, however, disadvantageously brings about supply of oxygen, thereby promoting the formation of rust.
Still further, when water injection for actually extinguishing fire is carried out, water pressurized at about 7 to 10 kg/cm2 flows from the feed pump into the secondary pipelines upon opening of the valve section. If air remains at the corners or upper portions in the pipeline, however, an effective cross section of flowing water in the pipeline is reduced, which can unfavorably prevent water from flowing.
Even further, when water highly pressurized by the feed pump is supplied to the sprinkler heads which have not yet been actuated, air stored therein beforehand is compressed to become high pressure air, thereby causing such a danger that elastic force of the high pressure air can blow off components of the sprinkler heads. In addition, when a fire actually breaks out, water cannot be discharged until the charged air is completely drawn off. As a result, it is pointed out that the dry-type sprinkler system is inferior to the wet-type sprinkler system in immediacy at an initial extinguishing operation which is the essential object of sprinkler systems.
To cope with the various inconveniences of the known sprinkler systems, particularly to enhance a rust prevention performance, an extinguishing fixture is proposed, for example, in Japanese Patent Kokai Publication Hie 10(1998)-234881. According to the extinguishing fixture, in place of air, inert gas is charged in a pipe portion of the secondary pipeline, at a location immediately above the sprinkler heads of the wet-type sprinkler system. By using inert gas such as nitrogen gas, rusting and development thereof can be effectively prevented in both the wet-type sprinkler system and the dry-type sprinkler system.
Further, there is disclosed a water flow detecting system for a wet-type sprinkler system, for example, in Japanese Patent Kokomo Publication No. Hie 7(1995)-12382, in which fluid in the secondary pipelines is brought to have a low pressure (but not negatively pressurized) than water in the primary pipelines. In this case, if a fire actually breaks out, the low-pressure water in the secondary pipelines is immediately discharged, so that it is considered that this system is effective for initial extinguishing operation.
However, in the above mentioned extinguishing fixture disclosed in Japanese Patent Kokai Application Hie 10(1998)-234881, in which inert gas has been charged, if the sprinkler head is actuated in a relatively small and tightly closed room, nitrogen gas fills the room, whereby the room undergoes oxygen deficiency, which can adversely affect safety.
Further, according to the invention disclosed by Japanese Patent Kokomo Publication No. Hie 7(1995)-12382, the immediacy of the initial extinguishing operation can be ensured. However, water is pressurized although the pressure degree is low. Therefore, damage caused by water injection is not avoidable when sprinkler heads function in a wrong way.
The present invention is proposed to eliminate the above inconveniences, and an object of the invention is to provide a wet-type sprinkler system which is capable of preventing damage to be caused by water when a sprinkler head functions in a wrong way, with ensuring to quickly perform an initial extinguishing operation of sprinkler heads at an actual fire.
To attain the above mentioned object, a wet-type sprinkler system according to claim 1 of the present invention has a negative-pressure-securing unit for maintaining water charged in at least one secondary pipeline of a feed pipe arrangement in a negatively pressurized. This negatively pressurized state is considered as a normal condition, namely xe2x80x9cready statexe2x80x9d, in the present invention.
As a result, even if sprinkler heads which are individually actuated in a wrong way to given an open state, water in the secondary pipeline can be prevented from being erroneously discharged, from the sprinkler heads. In other words, water in the secondary pipeline is maintained in the negatively pressurized state, so that air may be drawn into the opened sprinkler heads but water can never be injected from the sprinkler heads.
When a fire actually breaks out, a control section receives a fire-detection signal from a fire sensor, and causes a valve section to be opened and a water supply unit to start operation. Thus, water is conveyed from at least one primary pipeline to the secondary pipeline, whereby the pressure in the secondary pipeline is changed from the negatively pressurized state to a positively pressurized state. The system in such a preparatory movement (by the attainment of the valve opening) jets water through sprinkler heads by means of individual opening movements thereof.
In a wet-type sprinkler system as claimed in claim 2, there are provided a suction pipe communicating with the secondary pipeline of the feed pipe arrangement at a top part thereof, the secondary pipeline forming a water supply line from the water supply unit to the sprinkler heads, and a suction unit for sucking the internal part of the secondary pipelines which is provided at a top part of the secondary pipelines, the suction pipe and the suction unit forming the negative-pressure-securing unit. The water stored in the secondary pipeline which is normally filled with water is negatively pressurized due to the suction operation of the suction unit, and the negatively pressurized state is considered as a normal condition.
As a result, the negative-pressure-securing unit with a simple structure surely functions.
A wet-type sprinkler system as claimed in claim 3 comprises a water level detecting unit arranged at a top part of the secondary pipeline for detecting a water level in the secondary pipeline, wherein the control section controls the water supply unit and the opening and shutting of the valve section when the water level becomes lower than a predetermined level in response to a signal supplied from the water level detecting unit, to supply water from the primary pipeline to the secondary pipeline section.
By virtue of this construction in addition to the function as claimed in claim 1, the level of water in the secondary pipeline, which is negatively pressurized and accordingly likely to evaporate, can always be kept, whereby immediacy of the fire extinguishing system can be maintained.
Subsequently, the a wet-type sprinkler system as claimed in claim 4 has such a function that the control section controls the valve section so as to be opened only when the control section receives the fire-detection signal a plurality of times within a predetermined time period.
By virtue of this structure, in addition to the function as claimed in claim 1, it becomes possible to effectively prevent the secondary pipeline from being unnecessary relieved from the negatively pressurized state then to be positively pressurized by a mere wrong-way-function of the fire detecting unit.
According to a wet-type sprinkler system as claimed in claim 5, the suction pipe of the negative-pressure-securing unit is provided with a negative-pressure-regulating member for canceling excessive negative pressure of water caused by the suction operation of the suction unit. As a result, the pressure of water can be increased before the sucked water is brought to have an excessively negative pressure and accordingly evaporates to cause cavitation.
In a wet-type sprinkler system as claimed in claim 6, the negative-pressure-regulating member in claim 5 are implemented as a vacuum breaking valve which functions to increase the pressure of water, when the negative pressure becomes lower than a predetermined value. The vacuum-breaking valve has a single function for which troublesome setting is not necessary, whereby the negative pressure regulation can be achieved with a minimum cost without fail.